Frontier Airlines wants to expand its service to Mexico.
The low-fare carrier is seeking federal approval to add one nonstop flight from Cozumel to Denver, and nonstop flights from Puerto Vallarta to Salt Lake City and Kansas City.
The service would be offered three times a week on all routes.
Frontier hopes to get the go-ahead to start the new service in November.
Denver-based Frontier serves 48 destinations in 25 states and Mexico, from its hub at Denver International Airport.